1. Field of the Invention
The present invention relates to a printer for printing on a sheet.
2. Description of the Related Art
Ordinal printer is provided with a printing head for printing on a sheet of paper or the like, and with a carrier device for delivering the sheet. Ordinal carrier device is provided with a carrier belt wound between a pair of rollers. Using the carrier belt; the sheet of paper or the like is delivered to a printing position opposing the printing head, and is delivered from the printing position.
In order to print sheets with differing thicknesses, a type of printer has been developed that has a device allowing the adjustment of a gap between the carrier belt and the printing head in the printing position.
For example, a printer disclosed in Japanese Laid Open Patent Application Publication 2003-94744 is provided with a carrier belt unit. The carrier belt unit has a carrier belt wound between a driving roller and a driven roller. The carrier belt unit can be swung around a rotary shaft of the driving roller. The gap between the printing head and the carrier belt is increased or decreased by swinging the carrier belt unit around the rotary shaft of the driving roller.
In the conventional printer, the gap between the printing head and the carrier belt is adjusted by swinging the carrier belt unit around the rotary shaft (the rotary shaft of the driving rotor). If the printing head extends for a short distance along a delivery direction of the carrier belt (hereafter shortened to delivery direction), there is no particular problem in adjusting the gap between the printing head and the carrier belt by means of swinging the carrier belt unit.
However, if the printing head extends for a long distance in the delivery direction, this method of adjusting the gap by swinging the carrier belt unit is problematic. In a case of a printer in which a plurality of printing heads is aligned in the delivery direction, the actual distance along which the printing heads extend is long, and the problem of adjusting the gap becomes quite apparent.
When the printing head or heads extend for a long distance in the delivery direction and the gap between the printing head and the carrier belt is adjusted by swinging the carrier belt unit, a portion of the gap at a predetermined distance from the center of swinging can be adjusted to a determined value. However, the gap cannot be adjusted to the determined value at locations which do not have the same distance relationship with respect to the center of swinging. In the conventional printer, the carrier belt unit cannot be moved in a parallel manner, and consequently the gap cannot be maintained uniform when the printing head or heads extend for a long distance in the delivery direction.
In a color ink jet printer, for example, four ink jet heads are aligned in the delivery direction. A technique is required for adjusting the carrier belt position so that the gap between the carrier belt and each of the ink jet heads is maintained uniform, and this uniform gap can be increased or reduced.